Context-sensitive flow interrupter and drainage outflow optimization system

ABSTRACT

Embodiments of the invention provide methods and devices for improved drainage systems and tubing. In one embodiment, a context-sensitive flow interrupter is provided that inhibits or facilitates flow of fluid when engaged with a mating holder. In another embodiment, outflow is optimized through control of the pressure in gas pockets in a tube, drainage tube or assembly. In one such embodiment, gas pockets are vented to inhibit excessive back-pressure or suction on an organ, vessel or cavity being drained. In another such embodiment, loops in the tubes are avoided by using a mechanical template in the form of a groove or peg assembly to thread the slack in the drainage tube to generate a monotonic gradient. In another embodiment, such as for active drainage systems, a bypass channel is provided that allows an applied vacuum to go around an obstruction created by the collection of fluid in an undrained dependent loop.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 13/821,611, filed Mar. 8, 2013, which is a national stageapplication of International Application No. PCT/US2011/050810, filedSep. 8, 2011, which claims the benefit of U.S. Provisional ApplicationNo. 61/381,266, filed Sep. 9, 2010, the disclosures of each of which arehereby incorporated by reference in their entirety, including allfigures, tables and drawings.

BACKGROUND OF THE INVENTION

Current medical practice requires some body cavities, organs (e.g., thebladder or kidney), spaces (e.g., the pleural space), or wounds ofpatients to be drained of fluid whether in the liquid form (e.g., urineor blood) or gaseous form (e.g., air, gas) or a gas/liquid mixture(e.g., frothy exudate). For example, current medical practice includesdraining blood in a hemothorax and air, gas, or frothy exudate from apneumothorax.

Examples of urine drainage include urinary catheters inserted via theurethra, nephrostomy tubes, and suprapubic catheters. Nephrostomy tubesare inserted directly in the calyx of the kidney through the patient'sback to drain urine from the kidneys. A suprapubic catheter drains urineout of the bladder but is inserted directly into the bladder through theabdominal wall, instead of through the urethra.

Examples of chest and thoracic drainage include pleural drains that areinserted in the pleural space and drain air, gas, or blood or a mixtureof both from the pleural space via a chest tube and a chest drainagesystem, such as the Pleur-evac.

Examples of blood drainage include chest tubes for evacuating blood froma hemothorax, wound drainage catheters, and surgical drainagecollectors.

An example of mediastinal drainage includes a pericardial catheter thatdrains blood from the pericardium, the sac surrounding the heart.

Examples of gastrointestinal drainage include nasogastric catheters anddrainage tubing that empties into a collection vessel.

It is also widely accepted that to control infection, fluid that hasdrained from a patient should not be allowed to flow back to thepatient.

Also, a drainage system can be active or passive. A passive system canbe gravity-operated such as a urine drainage system. An example of anactive drainage system is a chest drainage system where a vacuum isapplied to the drainage system.

As one particular example, urinary catheters are commonly used forpatients who are undergoing surgery, incapacitated due to a spinalinjury or pelvic fracture, incontinent with open sacral or perinealwounds, or incapable of voluntary urination in order to permit thedrainage of urine. A urinary catheter, such as a Foley catheter, is aflexible, sterile tube that is inserted into the bladder via the urethrato allow the urine to drain into a collection receptacle. Foley bags area common drainage collection receptacle used to collect urine from aFoley catheter inserted in the urethra. Urine is transferred to thecollection bag via a drainage tube connected to the catheter.

A primary risk with urinary catheters is their contribution to urinarytract infections. A urinary tract infection (UTI) is considered a“never” event for which a hospital is not reimbursed by Medicare fortreatment costs and also cannot charge the expenses to patients.Therefore, there are incentives for hospitals to follow best practicesin order to avoid or reduce catheter associated UTI occurrences in theirpatients. Accordingly, as one guideline, the Center for Disease Control(CDC) recommends, at page 13 of the 2009 Guidelines for Prevention ofCatheter-Associated Urinary Tract Infections, to “keep the collectingbag below the level of the bladder at all times” (Category 1B). Thisguideline is to prevent backflow of urine to the bladder from thecollection receptacle by gravity.

To meet this recommendation, the drainage collection bag is usuallyhooked onto a support (such as a rail or hospital bed) at a locationbelow the level of the bladder. Most collection bags are also vented, sothat the intraluminal pressure of the receptacle and empty drainagetubing is at atmospheric pressure, which facilitates gravity dependentdrainage.

It is important for the collecting bag to be hooked below the level of apatient's bladder to help keep the flow of urine downhill towards thecollection bag. However, when transporting a patient, the drainagecollection bag is often placed on the patient's abdomen or on thetransport gurney instead of at the proper lower hanging location. Thisis usually performed to avoid rips and urine spills due to thecollection bag protruding from the gurney when at its proper hanginglocation.

A problem with placing the collection bag on the belly of the patient isthat when the bag is higher than the bladder, it is possible for urinein the bag or tubing to flow back to the patient. This backflow of urinecan cause infection and patient discomfort.

Although backflow is a recognized problem, on any drain bag or urinemeter bag available on the market, if the bag is squeezed, heldupside-down, or held above the level of the patient's bladder, it willnot stop 100% of urine from going backwards. Unfortunately, oneway-valves (non-return or non-reflux valves) cannot be used to preventback-flow of urine because the CDC Guidelines for Prevention ofCatheter-Associated Urinary Tract Infections (1981 and 2009) state thatan unobstructed flow of urine should be maintained.

The unobstructed flow of urine is important because when patients arecatheterized, many are passing blood and clots in their urine. In somecases, stones and sediment are passed by the patient. Further, there isoften viscous low output urine. If an anti-reflux mechanism or valve isin place, the danger is greater of impeding the free flow of urine andcreating a clogging effect at the anti-reflux mechanism. The cloggingeffect may cause a standing column of urine that may back right up intothe patient.

Recent anti-reflux chambers are designed to be an elevated dome chamberabove the bag with a right angle then leading into the drainage tubing,which minimizes urine from going back to the patient through thedrainage tubing. However, in certain orientations such as the refluxchamber being on the dependent side, the anti-reflux chamber fails andurine is still able to flow retrograde through the anti-reflux chamberand re-enter the drainage tubing.

Another problem with current urinary catheter and drainage bag systemsis that when the collection bag is hooked onto the support, the drainagetube between the catheter and the collection bag contains excess slack.As shown in FIG. 1A, this excess slack in the drainage tube 13 betweenthe catheter 14 and the collection bag 10 hooked onto the support 12(via hook 11) creates a loop (see encircled section), that serves as abasin into which fluid will pool. The term loop in this application willmean any loop, U-loop, and inflection point in a drainage assembly whereliquid can accumulate and/or obstruct a cross-section of the tubing.

When the fluid level within the loop rises to fill the tubing'scross-sectional area (see line at trough of FIG. 1B), two separateairspaces are formed (airspace U and D) and air pressure between the twoairspaces can no longer equilibrate across the fluid-filled Loop. Theair pocket upstream of the loop (airspace U of FIG. 1B) is effectivelytrapped because it cannot escape back toward the patient or downstreamto the drainage bag 10. As more urine flows out, the upstream meniscus Urises and compresses airspace U. Because the trapped amount of air inairspace U is being squeezed into a smaller volume by the risingmeniscus U, the pressure in airspace U rises and resists the rise ofmeniscus U. Thus, as more urine collects in the urine-filled loop,meniscus U barely moves up while meniscus D, which is exposed toatmospheric pressure via the vented collection bag, rises. The rise inpressure in airspace U generates a backpressure that is transmitted backto the bladder 20.

Because the bladder is highly compliant, the bladder responds tobackpressure by stretching and accommodating greater undrained urinevolumes, while maintaining low intravesical (bladder) pressure. Fluidwill accumulate within the bladder until intravesical pressure exceedsthe back-pressure caused by the air-lock obstruction of airspace U. Thepressure at airspace U equals the difference in elevation H betweenmenisci U and D. The maximum difference in menisci elevation across theloop effectively sets the pressure and bladder volume thresholds beforeurine can crest over the downstream (distal) apex and flow into thecollection bag. In-vitro tests have shown that back-pressures of 20 cmH₂O can exist due to a urine-filled loop. The relationship betweenbladder pressure and volume of urine in the bladder can be understood byreference to the cystometrogram of FIG. 2. As can be seen by the basalcystometrogram, a 20 cm H₂O backpressure on the bladder means that about425 ml of urine is trapped in the bladder. This high volume of undrainedurine is likely a risk factor for urinary tract infections.

Accordingly, there continues to be a need in the art for improveddevices and procedures for minimizing the instances of infections and/orreduce backflow or backpressure contribution to those instances ofinfections.

Although this background describes certain specific applications andproblems, embodiments of the invention should not be construed aslimited to or requiring the solving of all of these problems.

BRIEF SUMMARY

Embodiments of the invention provide methods and devices for improveddrainage systems. As described herein, methods and devices are providedthat can aid in controlling pressure within drainage systems. Certainembodiments of the invention can be applied to medical situations inorder to address problems with drainage and the resulting pressures feltby internal organs, such as the bladder.

Embodiments of the invention work with and can be adapted for bothpassive and active drainage systems as well as general purpose tubesother than drainage tubes where air locks and pressurized gas pocketscan develop that hinder free flow through the tubes.

In accordance with certain embodiments of the invention, acontext-sensitive flow interrupter is provided that can be used withinand outside healthcare applications to inhibit flow of fluids.

In one embodiment, the context-sensitive flow interrupter is used toaddress urine backflow occurrences in urinary catheter and drainagesystems, and includes a holding device for a collection bag of theurinary catheter and drainage system. According to a specific embodimentof the invention, a holding device for a Foley bag is provided (insteadof the hook currently used in practice) that automatically opens anormally closed clamp. The normally closed clamp is installed on thedrainage tube connecting the catheter to the bag or at any convenientlocation within the Foley assembly (catheter, drainage tube, and bag)where it can prevent backflow of urine when the clamp is closed ininstances where the drainage bag or drainage tubing is placed above thebladder. The clamp closes the tube or urine flow passage whenever theclamp assembly is not inserted into its receptacle that is mounted on anoperating room (OR) bed, a transport stretcher or gurney, a wheelchair,a procedure table, etc. When the clamp assembly is inserted into itsreceptacle to “hang” the Foley bag, the clamp is automatically openedproviding unobstructed flow to urine, blood, stones and sediments. It isalso contemplated that other flow interrupters such as stopcocks, ballvalves, and cuffs can be used instead of a clamp.

Presently, a caregiver must hang the Foley bag at a location below thebladder of a patient. In addition, when transporting the patient, acaregiver often unhooks the Foley bag and moves the bag from its hangingposition. Therefore, with certain embodiments of the invention, no extrasteps are required to operate the flow interrupter. Rather, the processof “hanging” the bag automatically opens the clamp or stopcock of theflow interrupter. Similarly, the process of “unhooking” the bag from itsholder closes the clamp or stopcock, thereby inhibiting urine fromback-flowing from the Foley bag. Advantageously, no new motions arerequired to be performed and the caregiver does not need to remember todo anything other than what the caregiver is used to performing. Incertain embodiments, the process of milking the drainage tube can alsoactivate a context-sensitive flow interrupter which could be placed atthe proximal end of the drainage tube or at the site where loops aremost likely to form. In an embodiment, a context-sensitive flowinterrupter can be incorporated at or near the drainage bag.

The clamp or stopcock can be made of any suitable material. For example,the clamp can be made of spring steel or resilient plastics. Thestopcock can be a ball valve.

The holder for the flow interrupter and bag can be mounted on the OR bedor stretcher or transport gurney or wheelchair such that it holds theFoley bag in a way that the bag does not protrude from thebed/stretcher/gurney/wheelchair. In a further embodiment, the bagholder/flow interrupter opener can be mounted on a lockable swing armthat would allow the option to swing the Foley bag out so that the Foleybag protrudes from the OR bed in a manner allowing an anesthesiaprovider to read the volume of contents in the Foley bag via itsgraduated markings while standing at the anesthesia machine.

In other applications of the context-sensitive flow interrupter, theflow interrupter could be normally open instead of normally closed.

According to an embodiment where the context-sensitive flow interrupteruses a stopcock, the state (closed or open) of the stopcock is toggledwhen inserting into or removing from a holder.

According to certain embodiments of the invention, a drainage outflowoptimization system is provided to improve urine outflow and minimizeundesired backpressure or suction at the bladder.

In one embodiment, a system is provided that eliminates or substantiallyreduces formation of loops and inflection points where liquid cancollect to inhibit undesired generation of backpressure and/or suction.In another embodiment, a system is provided that minimizes backpressureand/or suction even in the presence of loops where liquid can collectand obstruct the tubing cross-section.

In a specific embodiment example, a mechanical template capable ofshaping a tube is provided to achieve a monotonic downward gradient of adrainage tube, reducing formation of loops. The mechanical template caninclude a zigzag groove, spindle or series of hooks or pegs. Because nomodifications to the drainage tube are necessary in order to adoptmechanical templates of embodiments of the invention, the subjectmechanical templates to shape a tube work with existing drainageassemblies, such as the standard Foley assemblies that are currently inuse. In certain embodiments, the mechanical templates can be provided inkits.

According to one embodiment of the subject mechanical templates to shapea tube, a groove can be provided on a holder. The groove can have azig-zag or some other pattern on the sloped plane. The Foley tubing canbe snapped into the groove ensuring that the Foley tubing has amonotonic negative (downward) gradient that will inhibit the formationof loops where liquid can collect. The groove can also be carved out ofa flat slab of material that is attached to an IV pole, OR bed,wheelchair, etc.

For embodiments incorporating the context-sensitive flow-interrupter,the clamp or stopcock or other flow interrupter can be inserted into areceptacle upon running the drainage tube through the mechanicaltemplate. A thinner walled drainage tube (as compared to the currentFoley tubing) may be used to allow the use of a lower-force clamp toocclude the drainage tubing as compared to that used for a thickerwalled drainage tube.

According to another embodiment, backpressure and/or suction isalleviated by a venting or bypass system in the drainage tube. Theventing system can provide a pressure adjustment along one or morelocations within the drainage tube or Foley assembly, including at thebladder itself. In the case of bladder venting, one or more ventinglumen that vent to atmosphere or other desired pressure is built intothe wall of the Foley catheter with vent ports at the vent tip orcatheter portion inside the bladder. The venting system can include aventing tube or bypass tube within the drainage tube or at least oneventing or bypass lumen extruded within a wall of the drainage tube.

When a multitude of venting lumens is used, the vent ports may besituated at different locations within the Foley assembly so that anygas pockets at the corresponding vent ports may be vented. A singlelumen extruded along the length of a drainage tube may also have amultitude of vent ports along its length that open to the interiorsurface of the drainage tube and/or its exterior surface depending onthe desired application.

The venting system can vent to atmosphere so that pressure in the ventedspace equilibrates to atmospheric pressure. It can also vent to apressure above atmospheric (supra-atmospheric) pressure or belowatmospheric (sub-atmospheric). If the Foley catheter is placed below thepatient's thigh, instead of above the patient's thigh as is usually thecase, there may be concern that the Foley catheter may create a slightundesirable siphon effect on the bladder. To counteract this potentialsiphon effect, airspace U (see FIG. 1B) may be vented to an adjustablesupra-atmospheric pressure. According to certain embodiments of theinvention, this supra-atmospheric pressure can be obtained viamechanisms such as a spring-loaded valve that only allows gas to flowwhen a desired pressure is reached, a ball of specific weight thatoccludes a flow passage and is lifted when the desired pressure isreached, thus allowing gas to flow, or a gas outlet immersed into waterwhereby the depth of immersion of the outlet below the water surfacedetermines the backpressure. Vents at the Foley catheter portion insidethe bladder (as previously described) that vent to atmosphere can beused to counteract a potential siphon effect on the bladder.

In a further embodiment, the venting system can incorporate abackpressure adjuster, where gas pockets in the drainage tube are ventedto a drainage receptacle vented at atmospheric pressure via a ventingtube. The drainage receptacle can contain fluid and may even be thedrainage bag. One end of the vent tube can be controllably immersed influid in the receptacle in order to adjust the backpressure.

While specific embodiments and features described herein are directed tourine drainage and Foley assemblies, which provide concrete examples offluid backflow prevention and fluid outflow optimization, theapplicability of embodiments of the invention to other drainageapplications such as urine, chest, blood and mediastinum drainage andactive and passive drainage systems as well as non-drainage tubing inlight of the embodiments of the invention described herein should bereadily apparent.

It should be understood that although this Summary presents selectedconcepts and features described in more detail in the DetailedDescription, it should be understood that the Summary is not intended toidentify key features or essential features of the claimed subjectmatter or to limit the scope of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show a typical urinary catheter and drainage bag systemand illustration of airspace backpressure formation.

FIG. 2 shows a typical cystometrogram, the compliance curve for thebladder.

FIGS. 3A, 3B and 3C show representations of a context-sensitive flowinterrupter according to an embodiment of the invention.

FIGS. 4A and 4B show representations of a context-sensitive flowinterrupter according to another embodiment of the invention.

FIGS. 5A and 5B show representations of a context-sensitive flowinterrupter with a spring clamp configuration according to an embodimentof the invention, where FIG. 5A shows the normally-closed position andFIG. 5B shows the open position.

FIGS. 6A-6D show representations of a context-sensitive flow interrupterusing a deformable resilient material according to an embodiment of theinvention, where FIGS. 6A and 6C show the normally-closed position andFIGS. 6B and 6D show the respective open position.

FIGS. 7A and 7B show representations of a context-sensitive flowinterrupter using a stopcock according to an embodiment of theinvention.

FIG. 8A shows a representation of a chest drainage system.

FIG. 8B shows a chest drainage system with an external bypass accordingto an embodiment of the invention.

FIG. 8C shows a chest drainage system with an external bypass accordingto another embodiment of the invention.

FIG. 9 shows a representation of a backflow optimization system with amechanical template according to an embodiment of the invention.

FIGS. 10A-10C show representations of mechanical templates to shape adrainage tube in accordance with certain embodiments of the invention.

FIG. 11 shows representations of a backflow optimization system withvent with (B) and without (A) gas-permeable membrane according to anembodiment of the invention.

FIGS. 12A and 12B show representations of a system utilizing acorrugated hose in accordance with an embodiment of the invention.

FIGS. 13A and 13B show representations of a venting system with aventing collar according to an embodiment of the invention.

FIG. 14 shows a representation of a venting/bypass system with internalventing/bypass tube according to an embodiment of the invention.

FIGS. 15A-15C show representations of a venting/bypass system withextruded venting/bypass lines according to an embodiment of theinvention.

FIG. 16A shows a representation of a general purpose tubing with aquasi-continuous venting strip according to an embodiment of theinvention.

FIG. 16B shows a representation of snap-on lumens for a quasi-continuousventing strip according to an embodiment of the invention.

FIG. 17 shows a representation of a venting/bypass system with internalventing/bypass tube according to an embodiment of the invention.

DETAILED DISCLOSURE

Embodiments of the invention provide methods and devices for improveddrainage systems. The subject methods and devices can be used within andoutside healthcare applications to contextually inhibit flow of fluidsand/or optimize fluid outflow. Within the healthcare applications, thedrainage systems can be for body cavities, organs, spaces, or wounds.

Certain embodiments of the invention are directed to minimizinginstances of urinary tract infections by effective means of inhibitingurine back-flow from a drainage bag back to the patient and minimizingundesirable back-pressure and/or suction. Although embodiments directedto urinary catheter drainage systems are described in detail herein, thesubject devices and methods can be applied to other fluid systemsoutside of urinary catheter drainage systems, and even outside ofmedical applications, where optimization of drainage or outflow andcontext-sensitive control of fluid flow are desired.

In current practice with respect to urinary catheter drainage systems,because Foley bags and connecting tubing are generally hung from thepatient's bed, there is almost inevitably a loop of the drainage tubingthat hangs below the collection bag and allows liquid to accumulate andcreate the possibility for a water trap, airlock, and backpressure thatis transmitted to the bladder and renal system. Currently, someclinicians will take the time to empty the accumulated urine out of theurine drainage tubing while others may not. The urine is emptied bylifting the drainage tubing so that the accumulated urine can flow bygravity into the collection bag. This process of emptying the drainagetubing is sometimes called “milking”. During milking, there is also thepossibility of retrograde flow of urine from the drainage tubing back tothe bladder if the tubing is raised above the bladder level or apressure gradient is established that promotes retrograde urine flow.

During and/or after milking there is also the possibility ofestablishing a sub-ambient pressure (suction), which may cause bladdertissue to wrap around the tip of the Foley catheter and cause trauma.Referring again to FIG. 1B, one visual for determining that suction isoccurring (with sub-ambient pressure at airspace U) is when meniscus Uin the upstream leg is higher than meniscus D in the downstream leg ofthe tubing.

In accordance with an embodiment of the invention, a context-sensitiveflow interrupter is provided that can inhibit back flow of urine from adrainage bag when the drainage bag is not properly secured or duringmilking of the drainage tubing, i.e., emptying the drainage tubing ofaccumulated liquid. Although the subject context-sensitive flowinterrupter is described herein for addressing problems with urineback-flow, embodiments of the invention are not limited to suchapplications. For example the context-sensitive flow interrupter can beimplemented for any application where fluid is to be inhibited fromreturning to its source or flow is to be interrupted at certain timeswhile providing unobstructed flow at other times.

In one embodiment, the context-sensitive flow interrupter has twoparts—a holder portion and an actuator portion—that when interacted forma context-sensitive flow interrupter that can inhibit flow of fluid. Theactuator portion of the flow interrupter can be a clamp that functionsas a normally closed clamp. Therefore, unless the actuator portion isinter-locked with the holder portion, fluid cannot flow between thedrainage bag and the drainage tubing. The holder can have a receptaclefor the actuator portion of the flow interrupter. When the actuatorportion is inserted into the holder, the normally closed function of theactuator portion is released and fluid flow is unobstructed. Thedrainage tubing can have a section of tubing particularly adapted forthe actuator portion of the flow interrupter.

According to one embodiment, such as shown in FIG. 3A, the section oftubing 20 particularly adapted for the actuator portion of the clamp 30allows for an external jaw 31 to be affixed that has a spring mechanism32 keeping the jaw 31 closed and the section of tubing 20 in a clampedposition. Arms 33 can extend from the jaw 31, the arms 33 beingconnected to the spring mechanism 32 such that bringing the armstogether causes the spring mechanism to open the jaw 31 and thereby openthe section of tubing 20. The arms 33 can include handles 34, which canbe ergonomically formed for ease of use. The actuator portion of theclamp 30 can be made of any suitable material. For example, the springmechanism 32 and the arms 33 and jaw 31 of the actuator portion of theclamp can be made of spring steel or resilient plastics.

According to one embodiment shown in FIG. 3B, the holder portion of theclamp 30 can have a receptacle in the shape of two rods 41 protrudingfrom the side of the holder portion 40 such that when the actuatorportion with clamp 30 is inserted downward, between the two rods 41, thespacing between the two rods 41 cause the handles 34 (or arms 33) of theclamp 30 to come together and thereby opens the clamp 30 (FIG. 3C). Inone embodiment, the rods 41 have concentric rollers inserted over themto assist in insertion. The handles 34 (or arms 33) may also havenotches (not shown) that positively and securely engage the rods/rollersto create a detent position when the clamp 30 is fully inserted in theholder. For illustration, the bag is shown attached to the clamp by astring that allows the bag to hang from the clamp when the clamp ininserted in its receptacle. This also fixes the location of the tubingrelative to the clamp. Other means of attachment of the bag to the clampare possible including a keyed means that would make it difficult tohang or attach the bag on anything else but a holder having a mate to akey portion associated with the bag.

According to another embodiment, as shown in FIG. 4B, brackets 42 can beused to cause the actuator portion of the clamp 30 to open. The brackets42 can be disposed so that the actuator portion is insertedperpendicular to a vertical axis (FIG. 4A).

The holder portion receptacle can be mounted on an OR bed, a transportstretcher or gurney, a wheelchair, procedure table, or other apparatus.When the clamp assembly is inserted into its receptacle to “hang” theFoley bag, the clamp is automatically opened providing unobstructed flowto urine, blood, stones and sediments. The holder for the clamp and bagcan be mounted on the OR bed or stretcher or transport gurney orwheelchair, such that it holds the Foley bag (or other drainagecollection receptacle) in a way that the bag does not protrude from thebed/stretcher/gurney/wheelchair. In a further embodiment, the bagholder/clamp opener can be mounted on a lockable swing arm that wouldallow the option to swing the Foley bag out so that the Foley bagprotrudes from the OR bed in a manner allowing an anesthesia provider toread the Foley bag while standing at the anesthesia machine.

According to another embodiment of the invention, the section of tubingof the actuator portion of the context-sensitive flow interrupter isformed with elastic/deformable yet rigid material on the outer walls ofthe tubing, within the walls of the tubing, or as a separate section oftubing that wants to remain in a collapsed position (i.e., touchingtogether) until released by the holder.

In one embodiment as shown in FIGS. 5A and 5B, the releasing mechanismcan be similar to the jaw opening spring clamp. According to anembodiment, a spring mechanism such as spring form 51 is disposed arounda section of tubing 50 to cause the tubing to be in a collapsedposition. Two rigid beams 52, or arms, are externally attached to thespring form 51, such that when the tubing portion is inserted into theholder, the two arms 52 come together at their distal ends, forcingtheir proximal ends to spread open and cause the spring form 51 tospread and the collapsed section of tubing to open as shown in FIG. 5B.The section of tubing that the arms connect to can be flexible and/ordeformable, allowing for a clamping effect without causing damage to thetubing.

In another embodiment, as shown in FIGS. 6A-6B, resilient material 61can be disposed at the outer walls of a section of tubing 60 a. Theresilient material 61 prefers to be in a position that causes thesection of tubing 60 a to close. When rigid arms 62 attached to, orconnected with, the resilient material 61 are pivoted inward, theresilient material moves with the rigid arms and may pop out to allowfor a circular cross-section. In yet another embodiment, as shown inFIGS. 6C-6D, the section of tubing 60 b having the rigid arms 62attached can be formed of a resilient material that prefers to be in acollapsed position. Then, the pivoting of the rigid arms 62 causes thesection of the tubing 60 b to be forced in an open position. The rigidarms can be affixed to the section of the tubing with a portion alongthe cross-sectional circumference of the section of tubing. The portionof the rigid arm 62 along the cross-sectional circumference of thesection of tubing can extend to the extent necessary to keep the sectionof tubing open and allow unobstructed flow of urine.

According to another embodiment, the context-sensitive flow interruptercan be in a form of a stopcock. For example, referring to FIG. 7B, astopcock 70 can be provided in which a turn of its handle or lever 72opens and closes a path between the drainage tube and a collection bag.In one embodiment, a spring mechanism can be attached to the handle suchthat the handle causes the stopcock to remain closed (or alternativelyto remain open) until the actuator section is received by the holder. Byinserting the actuator section into the receptacle on the holder 74, thereceptacle can cause the handle to turn and remain in a position wherebythe stopcock is open (or closed), such as shown in FIG. 7A.

The section of tubing having the actuator portion of the subject flowinterrupter can be disposed at or near the connection of the drainagetube to the drainage bag. The actuator portion can be disposed at ornear where the hook is disposed in present Foley bags and replace thehook and string.

According to the CDC guidelines, a caregiver must hang the Foley bag ata location below the bladder of a patient, and therefore currently hooksthe Foley bag to the bed or wheelchair of the patient. However, whentransporting the patient, a caregiver often unhooks the Foley bag andmoves the bag from its hanging position. The subject context-sensitiveflow interrupter performs its function as the caregiver hangs andremoves the Foley bag from its location at the bed or chair of thepatient. Therefore, no extra steps are required to operate the clamp.Rather, the process of “hanging” the bag automatically opens the clamp(or stopcock or other flow interrupter). Similarly, the process of“unhooking” the bag from its holder closes the clamp (or stopcock orother flow interrupter), thereby inhibiting urine from back-flowing fromthe Foley bag. Advantageously, no new motions are required to beperformed and the caregiver does not need to remember to do anythingother than what the caregiver is used to performing.

As previously described, the currently used combination of a Foleycatheter, drainage tube and collection bag can elevate the pressure inthe drainage tube and potentially the patient's bladder, which may inturn inhibit renal function. Specifically, a Foley assembly generallyincludes a) a Foley catheter inserted into the urethra, b) a drainagereceptacle or collection bag (also referred to as a Foley bag) thatcollects the urine and is vented to atmosphere and c) drainage tubingthat channels flow from the Foley catheter to the Foley bag. Foley bagsare usually hung under a patient. The excess length of drainage tubingwill usually form a loop while in clinical use. Such loops can bereferred to as dependent loops. When filled with urine, the loop forms awater trap. In order for liquid to flow from the bladder into the Foleybag in the presence of a urine-filled loop, the urine in the drainagetube must be lifted up and over the downstream leg of the loop.

In accordance with the principles of hydrostatics, the fluid pressure atequilibrium in the Foley catheter distal tip indicates that the bladderpressure is equal to the pressure in the air column (airspace U) of thedrainage tube minus the vertical elevation (in units of length of urine)of the Foley catheter's distal tip with respect to the bladder. Inpractical terms, the pressure in the bladder may be slightly less (onlya few cm H₂O) than the pressure in the air column. This pressuredifference may be dependent on whether the Foley catheter portionexternal to the patient is routed above or below the patient's thigh.

The pressure (or suction) in the compressed airspace U is indicated bythe difference H in meniscus elevation between meniscus U and meniscus Das shown in FIG. 1B. In one embodiment of the invention, a device isprovided to measure the difference H and thus the backpressure (orsuction) on the bladder (and through the cystometrogram, the retainedundrained urine volume). In a specific embodiment, the measuring deviceis in the form of a sheet with a grid of known spacing. In anotherembodiment, the measuring device is in the form of a perpendicular rodwith a graduated movable scale and two adjustable horizontal slidersthat are slid to the level of the menisci so that H can be readilymeasured. In yet another embodiment example, the measuring device is inthe form of a laser measuring device that reads the elevation of eachmeniscus and then calculates H by subtracting the lower elevation fromthe higher elevation.

In-vitro experimental tests established that the maximum pressure in theair column in the upstream leg of the loop must be high enough to pushthe column of urine up and over the lip or apex of the downstream leg ofthe loop. The pressure in the air column in the upstream leg of the loopthat forces urine up the downstream leg of the loop and into thedrainage bag is experienced as backpressure on the bladder, and maythus, in turn, affect the patient's renal system. In particular, theincreased pressure in the air column exerts a backpressure on thebladder and may thus inhibit normal bladder and/or kidney function.Outflow from the bladder is significantly augmented when the drainagetubing is “milked”, i.e., cleared of the urine collected in the loop,thus effectively removing the back pressure on the bladder and allowingit to empty.

Referring again to FIG. 1B, the urine collection bag hanging under thepatient results in formation of a loop in the drainage tubing and allowsfor the formation of a liquid trap in the bottom of the loop. As urineenters the tube, gravity causes it to pool in the bottom of the trap;the level quickly rises and blocks the cross-section of the tube. Thefluid in the bottom of the trap is bounded by two menisci—an upstreammeniscus and a downstream meniscus, respectively. The height of thedownstream meniscus is limited by the height of the downstream leg ofthe loop (the height of the distal apex).

In addition, because the Foley catheter is of sufficiently smallinternal diameter that it “gets wet and stays wet,” with a resultingcolumn of fluid held by the Foley catheter, at the downstream end ofthis column, there is a meniscus that is referred to herein as the Foleymeniscus—meniscus F. Between the Foley meniscus F and the upstreammeniscus U there is an airspace U, which can occupy most of the upstreamleg of the loop. Newly arriving urine that trickles down the descendingleg of the drainage tube (i.e., “open” channel flow) merges with thefluid in the bottom of the trap. The pressure in airspace D (the airpocket above the downstream leg of the loop) is atmospheric pressurebecause it is in pneumatic connection to the Foley bag that is vented toatmosphere. As incoming urine is added to the loop, the urine will tryto distribute equally between the two legs of the loop. However, asmeniscus U rises through the addition of urine, the fixed mass of air inairspace U is forced to fit into a smaller volume and is thuscompressed. As a consequence, the pressure in airspace U rises as moreand more urine flows into the loop. The pressure in airspace D remainsconstant at atmospheric pressure. Thus, the difference in pressuresbetween airspaces U and D drives the meniscus D up the downstream leg asshown in FIG. 1B. The difference in pressures in cm H₂O (or moreaccurately in cm of urine) between airspaces U and D is the heightdifference in cm between menisci U and D.

As previously mentioned, a urine-filled loop may place as much as 20 cmH₂O backpressure on the bladder, which means that about 425 ml of urineis trapped in the bladder of a typical adult patient (point B). However,clinicians have worked on the assumption, which is flawed, that apatient who has a Foley assembly is at the ˜20, 0 coordinate (point A)on the plot of FIG. 2 -, i.e., an almost empty bladder. However, due tothe back-pressure caused by loops, the catheter does not always drainthe bladder completely. Therefore, the current standard drainage tubeand drainage collection systems lead to a high incidence of largeresidual urine volumes due to this loop back pressure phenomenon.

Moreover, the prevalence of dependent loops and undrained dependentloops in clinical environments has been quantified and appears to be areal healthcare issue. In a prevalence study in a tertiary carehospital, 76 of 88 (87%) urine drainage systems in use with patients hada dependent loop. Of the urine drainage systems with dependent loops,84% had undrained fluid in them with differences in meniscus elevationas high as 26 cm, indicating back pressures as high as 26 cm H₂O beingapplied to the bladder.

The common clinical practice of lifting the loop, moving or milking thetube, or “walking the fluid” down the tube may or may not solve theproblem of backpressure formation. This is because the same conditionmay develop again, over time, leading to the same backpressure, or asiphon can form that may undesirably transmit negative pressure orsuction to the bladder.

Accordingly, certain embodiments of the invention are directed tooutflow optimization of drainage systems. By equalizing the pressures inairspaces U and D inside the drainage tube, the bladder can be protectedfrom high backpressure and difficulties in emptying. In one embodiment,backpressure is alleviated in drainage tubes by preventing the formationof loops where liquid can collect through the creation of a monotonicdownward gradient. In another embodiment, backpressure is alleviated indrainage tubes by venting the trapped, compressed air in an upstreamportion of a drainage tube to atmosphere, supra-atmospheric pressure orsub-atmospheric pressure.

In accordance with certain embodiments of the invention utilizingventing for control of pressure and fluid drainage, the vents aretwo-directional. That is, gas or air flow is able to travel in twodirections—into and out of the drainage tube. The two-way directionalitycan be achieved by using gas-permeable membranes. The bi-directionalityof flow allows pressure within the drainage tube to be relieved byallowing gas to flow out of the drainage tube but, contrary to aunidirectional valve, also allows gas to flow into the drainage tube,for example, air from the atmosphere to relieve unwanted suction orsub-ambient pressure.

In a chest tube application, as shown in FIGS. 8A-8C, a vacuum sourcewould be applied via a chest drainage system 80 to a drainage tube 81,such as a thoracic drain tube, connected to a chest tube inserted in thepleural space 82 of a patient. The chest tube is intended to transmitand maintain a negative pressure (slight vacuum or sub-atmosphericpressure) in the pleural space in which it is inserted. In clinicalpractice, it is observed that the chest drainage tube will also formliquid-filled loops 83 and that just like in FIG. 1B, the downstreammeniscus is higher than the upstream meniscus indicating that thepressure in the upstream air pocket is higher than the vacuum applied atthe chest drainage system 80. This formation of liquid-filled loops inchest drainage assemblies leads to the manufacturers' recommendationthat clinicians “milk” the chest drainage tube, i.e., empty theliquid-filled loop, similar to “milking” a urinary drainage tube.According to an embodiment of the invention such as shown in FIG. 8B, aventing port is provided at the upstream air pocket to connect theupstream air pocket to the vacuum at the chest drainage system via abypass lumen 85 (that bypasses the liquid-filled loop) in order to helptransmit the vacuum to the chest tube in spite of the water trapgenerated by the liquid-filled loop. A hydrophobic or other suchliquid-repellent, but gas permeable membrane can be disposed at theventing port to inhibit a given liquid or liquids from entering thebypass line. The particular gas-permeable membrane can be selected basedon the liquid needing to be repelled. For example one gas-permeablemembrane may be suitable for water, another for blood, and yet anotherfor urine. In a further embodiment such as shown in FIG. 8C, the ventingport to bypass lumen 85 is provided in plurality.

In one embodiment, the patient-side drainage tubing/bypass channelconnection is disposed higher than the distal apex 87 at the canisterside (or drainage bag side for urinary drainage systems). In such aposition, if fluid accumulates in the dependent loop 83 as in theexample of FIG. 8C and is left undrained for long periods of time, themaximum height that the patient side meniscus reaches will be limited tothe height of the distal apex 87. Further fluid collection after thecanister side meniscus has reached the distal apex 87 results in liquidflowing into the drainage canister as in FIG. 8C. By placing at leastone of the patient-side drainage tubing/bypass channel connectionshigher than the distal apex in the configurations in which a chestdrainage system is clinically used, then the membrane of the at leastone bypass channel connection may be able to avoid blockage fromstanding bodies of liquid.

Similar to the urine drainage systems, the catheter/drainage tubingcombination in a chest drainage system may make a small convex curve asthe catheter/drainage tubing leaves the patient as shown in FIG. 8C. Ifthe location of a sole patient-side drainage tubing/bypass channelconnection is on the ascending limb (such as venting port A in FIG. 8C)and the ascending limb is filled with liquid as shown in FIG. 8C, thebypass will not work. If the patient-side drainage tubing/bypass channelconnection is on the descending limb (such as venting port B in FIG.8C), the likelihood of the venting port being submerged or adjacent to abody of liquid is decreased because there is less probability of liquidaccumulation in the descending limb at vent B. Therefore, the likelihoodthat the bypass will be able to work as intended is substantiallyincreased if the connection is at the descending limb. Because the exactlocation of the descending limb cannot be determined a priori in chest,urine and other drainage systems, a multitude of vents and/or bypassconnections increases the probability that one of the vents and/orconnections will be at location free of liquid. A multitude of vents andconnections also allows more than one air or gas pocket to be vented ifthere is more than one air or gas pocket. By providing multiple ventingport locations as described with respect to certain embodiments, it ispossible to improve the performance of the bypass line or venting lumen.

In-vitro experiments conducted in association with prototype embodimenttests have shown that, in drainage systems, there is also a vacuum orpressure loss or perturbation across the drainage catheter if there isfluid accumulation in the catheter (as distinct from the drainagetubing) or an ascending limb of the drainage tubing. The pressure orvacuum change in units of cm H₂O at the catheter and/or drainage tubingis equal to the vertical elevation (in cm) of the column of liquid, whenthe liquid is water or has a density close to the density of water. Forexample, the fluid accumulation in the catheter and/or an ascending limbof the drainage tubing is shown in FIG. 8C as it relates to the chestdrainage example. According to an embodiment, for the purpose ofdetermining, estimating, compensating or adjusting the pressure orvacuum at the location or organ being drained, it can be helpful tomeasure the vertical elevation spanned by the two menisci of the body ofliquid at vent A in FIG. 8C and factor that loss in the calculation,measurement or remedial action or to configure the drainage system sothat liquid cannot accumulate in the catheter and/or the drainage tubingimmediately adjacent to the catheter.

For certain of the embodiments having multiple venting port locations,the multitude of vents can be provided as multiple vents along thedrainage tubing, as a drainage tubing with a strip of a gas-permeablemembrane along its length, or as a drainage tubing with a smallerinternal tube made of a gas-permeable membrane. In one embodiment, aventing channel separated from the interior of the drainage tubing by agas permeable membrane or a conduit made of the gas permeable membranecan extend at least a third of the distance of the drainage tube,enabling gas/air to vent along the interior of the drainage tube. Thelength of the channel or conduit can be such that the channel or conduitdoes not extend to the ends of the drainage tubing or only extends toone end of the drainage tubing. These above described configurations canbe used to ensure that a drainage system has a working vent to inhibitthe formation of undesirable backpressure or suction during clinicaluse, irrespective of the configuration of the drainage system (see alsoFIGS. 14, 15A-15C, 16A, 16B and 17 and the description related thereto).

If the chest tube is inhibited from transmitting a vacuum by theliquid-filled loop, complications such as unnecessarily extended lengthof stay, low blood pressure, and emergency surgery may arise. Forexample, recent data suggests that, in cardiac surgery patients, chesttube use is associated with longer lengths of stay (average 23.7 days)compared to patients who did not have a chest tube (average 10.4 days).

One possible reason for this difference in lengths of stay may beattributed to residual pneumothorax. A residual pneumothorax is apneumothorax (PTX) that persists after chest tube placement instead ofbeing resolved by the chest tube drainage.

Current procedures involve taking a daily supine anteroposterior chestX-ray of a patient with a chest tube to assist in chest drainage tubemanagement. The criterion for chest tube removal generally depends onthe indication for the chest tube placement. If the patient needed thechest tube because of PTX, the chest x-ray will be evaluated each dayfor the presence or absence of the PTX. In addition, the chest drainagecanister is checked for the presence of an air leak. To check thedrainage canister for an air leak, the suction on the container is heldand the patient is asked to cough (increasing intrapleural pressure).The existence of an air leak is signified by the presence of bubbles inthe water chamber of the drainage canister and means that air is stillescaping from the lunch parenchyma. In such a case, the chest tubecannot be removed. However, if the chest x-ray demonstrates no PTX andthere is no air leak, then the tube will be removed and a follow upchest X-ray is performed to determine that no PTX was caused by removalof the tube.

The decrease of the applied suction by the undrained fluid in adependent loop may predispose a patient to unresolved PTX. If theundrained dependent loop causes less suction, then the amount of vacuumset for the drainage system is not actually being applied to theintrapleural space. In addition, the current routine of performing dailysupine anteroposterior chest X-rays may not be the best or mostsensitive test for residual PTX.

However in another approach, if the indication for the chest tube wasdrainage of fluid, then the daily chest X-ray can be evaluated for thepresence of fluid. The amount of daily drainage is assessed and, ingeneral, if the chest tube output is less than 200 ml and the chestX-ray demonstrates little to no effusion, then the tube is pulled.However, if the chest tube output is greater than 200 ml, the tube isusually left in so as to avoid having to reinsert a tube due tore-accumulation of effusion. Here again, the reduction in transmittedvacuum from the undrained dependent loop may lead to reduced effusionthat is not a sign of patient improvement, but a result of reducedsuction, leading to decreased exudate being suctioned out of the lungs.

Because the average cost of a non-admission hospital day in the US isestimated at $3000/day, reducing the length of stay saves substantialcosts. Therefore, certain embodiments of the invention can be applied tochest drainage systems in order to improve the appropriate vacuum beingapplied at the intrapleural space to remove fluid.

In further embodiments, the venting port/bypass lumen can also be usedto equalize the pressure between an upstream air pocket and a downstreamair pocket when the vacuum is no longer applied, as in the case whereactive drainage is no longer being performed prior to removing the chesttube. This may help reduce problems during removal of the chest drainagetube. Among other implementations, the bypass lumen can be implementedin the same way as the venting lumen for the urine drainage system,i.e., as an internal separate lumen, an external lumen that is separateor attached to or extruded with the drainage tube or extruded in thewall of the drainage tube.

In addition, certain embodiments of the invention can be implemented toaddress the difficulty in ascertaining the actual vacuum being deliveredin a chest drainage (or other) system. For example, some current chestdrainage canisters include a device to indicate the vacuum beingdelivered. However, this device is misleadingly labeled “Patientpressure.” It is misleading because, due to the interference ofundrained dependent loops with passive and active drainage systems, itis clear that the pressure measured at the canister does not reflect thepressure at the chest drainage catheter tip.

Accordingly, certain embodiments include a sensor for measuring pressureby sampling pressure at the catheter tip. As one approach, a small borepressure sampling tube can be used to measure pressure at the cathetertip. However, in certain situations this tube gets clogged with fluidand may not measure the pressure reliably. Therefore, according to oneembodiment, one or more inexpensive, disposable solid state pressuresensors can be provided at or near the tip of the catheter to relay thepressure reading back by wire or wirelessly. In certain embodiments, thepressure senor and the wire(s) are imbedded in the wall of the catheter.The pressure sensor can be a MEMS-based pressure sensor or othersemiconductor or CMOS process-fabricated design.

According to an embodiment, a system is provided that can prevent theformation of loops where liquid can collect and ensure a monotonicdownhill gradient or at least prevent uphill gradients on the way to adrainage receptacle. Such systems can ensure free, unimpeded flow ofurine that may be especially important for newly transplanted kidneys.Of course, other applications are contemplated.

A monotonic downhill gradient is not necessarily a constant gradient. Ina coordinate system where the horizontal is x and the vertical is y, amonotonic gradient can be defined as a gradient where the secondderivative of y with respect to x (d²y/dx²) is never zero, i.e., thereis no inflection point in the drainage tubing. The first derivative of xwith respect to y (dy/dx) can be zero, i.e., portions of the gradientcan be horizontal. With a monotonic downward gradient, no downstreampart of the tubing will be higher in elevation than any upstream part ofthe tubing. As a result: (a) no urine-filled loops will be formed thatthrottle urine outflow and (b) no urine will collect in the tubing thatcan flow back to the bladder if the tubing is inadvertently placed abovethe bladder.

In accordance with one embodiment of the invention, in order toeliminate or substantially reduce formation of loops where liquid cancollect or obstruct the tubing cross-section, the drainage tubing isconfigured so that there is a monotonic downward gradient from thebladder to the Foley bag.

In certain embodiments, the system can include mechanical templates thatcan be mounted on IV poles, OR beds, stretchers, gurneys, patienttransport devices, wheelchairs, etc. that ensure that each downstreamelement of the drainage tubing is lower, or not higher, than theadjacent upstream component. In a specific embodiment, the mechanicaltemplate to shape a tube can be in the form of a groove for threadingthe drainage tube. For example, mechanical templates can be providedwith spiral, zig-zag shapes, or grooves that make the drainage tubingconform to the requirement that no downstream element is higher inelevation than an upstream element.

Referring to FIGS. 9 and 10A-10C, backpressure can be alleviated byproviding a monotonic downward gradient of the drainage tube flow. Themonotonic downward gradient can be accomplished by threading theexisting drainage tube of a Foley assembly on pegs provided at or nearthe hook for the Foley collection bag, such as shown in FIGS. 9 and 10A.The pegs can be straight or hooked. The pegs can also be providedextending out at an upward angle so that the drainage tube can catch onthe peg and be inhibited from sliding out. Advantageously, the pegassembly provides a mechanism that only requires the caregiver to useone hand because no snaps or bands are required to keep the tube inplace.

According to another embodiment, as shown in FIG. 10B, a bracketassembly can be provided to thread the drainage tube into the monotonicdownward gradient. The bracket assembly can include a lip along theouter edge to keep the drainage tube from sliding out. In yet anotherembodiment, a groove assembly can be provided as shown in FIG. 10C intowhich the drainage tubing is snapped.

For embodiments also incorporating the subject context-sensitive flowinterrupter, the holder portion can be provided at or near themechanical template.

In a further embodiment, the mechanical template can include additionalfeatures such as holders for alcohol swipes, a slot for smart phoneswith inclinometers, and a built-in water level.

To the extent that the templates can inhibit accumulation of liquid independent loops, milking, which may result in suction being applied tothe bladder, will likely not be performed. By avoiding creating asituation where milking could be used to alleviate the accumulation ofliquid, the templates can also reduce the likelihood of suction beingapplied to the bladder.

A corrugated hose 120, such as shown in FIGS. 12A and 12B, whose lengthcan be increased or shortened by extending or compressing thecorrugations respectively can also be used to take up any slack in thedrainage tubing to prevent the formation of loops and provide amonotonic gradient. Some corrugated hoses may maintain their shape whenthe corrugations are compressed. The corrugations can trap a smallamount of liquid at the trough of each corrugation. By making thecorrugations as small as possible, the amount of liquid trapped may beminimized. If it turns out that the small amount of urine trapped leadsto infection within x days, then this design may be recommended forsituations where it is known a priori that the Foley will be in placefor less than x days. This introduces the concept of drainage systemsoptimized for the expected duration of use instead of a “one size fitsall” drainage system.

A malleable (shape memory) drainage hose that retains its configurationand can be shaped to provide and retain a monotonic gradient is alsocontemplated. The hose may be made malleable through the material usedto manufacture it or a malleable insert could be embedded, extruded orattached with the drainage tube along part or all of its length.

Foley drainage tubing is currently thick-walled, presumably to preventkinking (that would create flow obstruction) when loops are present. Bypreventing the formation of loops where liquid can collect, it ispossible that the Foley tubing (or other drainage tubing) wall may beallowed to be made thinner because without loops, there is a less chanceof kinking. For example, if there is no slack in the drainage tubebecause the drainage tube is tidily shaped by a mechanical template,there is less chance of kinking. The thinner tubing walls can result inlower material costs. In addition, thinner walls may make it easier toconform the tubing to the pre-shaped grooves of certain embodiments ofthe invention. The drainage tubing does not necessarily need to be ofuniform wall thickness along its length, as is currently the case, andcould be of variable wall thickness along selected portions of itslength.

According to another embodiment, backpressure and/or suction isalleviated by a venting system in the drainage tube. In suchembodiments, there is no need to prevent loop formation because theventing system controls the backpressure and/or suction experienced bythe bladder (or other organ, space, or cavity).

The venting system can provide a pressure adjustment along one or morelocations within the drainage tube or Foley or drainage assembly. Theparticular locations can be based on where loops tend to form and/or ator near the Foley catheter or at the bladder itself.

The venting system can include a venting tube internal or external tothe drainage tube or extruded within a wall of the drainage tube. In oneembodiment, multiple vent tubes or lumens can be extruded within thewall of the drainage tube. The multiple vent tubes can be exposed to theinterior of the drainage tube at one or more locations along the tube orFoley assembly. The exposed openings can be protected with agas-permeable membranes that is hydrophobic or that can block urine orliquid or blood from flowing into the venting tube. An example of ahydrophobic gas-permeable membrane is PTFE membrane with 0.2 micronpores such as that used in the Millipore syringe filter (SLFG025NS).

Referring to FIG. 11, venting the airspace U to the atmosphere changesthe pressure and results in an equalization or an adjustment of pressurebetween the airspace U and the airspace D (as illustrated by the menisciof the fluid at the loop being about equal in height). This allows forimproved urine flow into the collection bag and better bladder emptyingbecause there is minimal backpressure (or unwanted suction) on thebladder and the operating point of the bladder has been moved fromapproximately coordinate B (425, 20) to approximately coordinate A(20,0) in FIG. 2.

In order to accomplish this adjustment, in one embodiment as shown inFIG. 11B, the airspace U in the drainage tube can be directly vented toatmosphere using a gas-permeable patch 120, for example, one similar tothat used on the Foley bag or the Millipore material. The port 121connected to the vent can be for example a slip fit port or Luer lockthat accepts tubing that is used to connect the vent port to atmosphere,supra-atmospheric pressure or sub-atmospheric pressure (as in the caseof a chest drainage system).

According to another embodiment of the venting port, a needledecompression kit can be provided that includes a sterile needle and adisinfectant for disinfecting the external surface of a drainageassembly where it will be punctured. This provides a quick way todecompress a compressed air pocket and vent it to atmosphere,sub-atmospheric pressure or supra-atmospheric pressure. In such anembodiment, a user can disinfect the external surface first and thenstab the needle through the tubing wall (that may be made of aself-sealing material) into the air pocket, allowing the pressure toequilibrate to atmosphere. Like the vent port, the needle can have aslip fit or Luer lock to connect to tubing that connects the ventedspace to the desired pressure.

As shown in FIGS. 13A and 13B, a venting collar 130 can be used to venta drainage tube 100 to atmosphere, supra-atmospheric or sub-atmosphericpressure. The venting collar 130 can be of different shapes (cylinder,sphere, rectangular, etc.). An opening 132 in the venting collar 130 canbe used to vent the drainage tube 100 to the atmosphere, the desiredpressure or to another chamber. The wrap-around or circumferentiallayout of the vent port 133 (covered with a gas-permeable membrane),ensures that the vent port 133 will vent irrespective of the location ofan air pocket if the drainage tube 100 is only partially filled withliquid. By having a wrap-around layout of an gas permeable membrane,problems with venting such as in a case where a cross-section ofdrainage tubing has both liquid and gas and the vent port was at onlyone location, which happens to be submerged (thereby inhibitingventing), can be avoided.

In another embodiment, the airspace U can be in pneumatic connection tothe inside of a vented collection receptacle. This can be accomplishedusing, for example, an external tube, an internal tube, or an inbuiltventing lumen embedded in the wall of the drainage tube.

In one embodiment, as shown in FIG. 14, an internal tube 141 can run aportion of the length of the drainage tube 100. In another embodiment,as shown in FIGS. 15A-15C, an inbuilt venting lumen can be embedded (orextruded) in the wall of the drainage tube and include an opening on theinterior surface of the drainage tube at the venting port locations. InFIG. 15C, the cross-section is made at the venting port 152 thatconnects to the interior of the drainage tube. The cross-section of theinbuilt venting lumen 150 in FIG. 15C can be of any appropriate shape orsize. The oval shape is shown as one possible cross-section that wouldfacilitate closing/crushing of the venting lumen when used with acontext-sensitive flow interrupter such as a clamp.

For the embodiments shown in FIGS. 14 and 15A-15C, the opening of theventing tube to the airspace in the drainage tube can include a membrane(see membrane 142 of FIG. 14) that blocks liquid from flowing into theventing tube.

In an embodiment, as shown in FIG. 17, instead of a membrane 142 at anopening of the venting tube 141 (as shown in FIG. 14), an internal tube241 can be provided having walls formed entirely, substantially, ormostly of a gas permeable membrane material. This internal vent tube 241can run at least a portion of the length of the drainage tube 100. Aplug 242 can be provided at an end of the vent tube 241 to inhibitliquid from entering the vent tube 241.

A drainage tube with the addition of a vent in accordance with anembodiment of the invention does not need to be manipulated or milked torelieve backpressure (or suction); in addition, tests of an embodimentof the subject vent indicate that no negative pressure or siphondeveloped.

In a further embodiment, a controlled back-pressure is applied to thesubject venting system to inhibit bladder collapse due to a potentialsiphon effect or to inhibit back flow during milking (emptying adrainage tube of accumulated liquid). In particular, the Foley cathetermay act as a siphon if its connection to the drainage tube is lower thanits entrance to the bladder, as is the case when a patient is layingflat and if the external portion of the Foley catheter is routed belowthe patient's thigh. This siphon action can pull a slight negativepressure on the bladder at the end of bladder emptying. Accordingly,certain embodiments of the invention provide a small amount ofbackpressure in the drainage tube to balance the siphon effect of theFoley catheter. According to an embodiment of the invention, the ventingtube includes a shunt having gas-permeable membranes at both ends.Placing the distal end of the shunt at a position below a few cm ofurine or other fluid, either in a special chamber inside or outside thecollection receptacle or by terminating it in the downstream leg of theloop will cause the pressure in the upstream leg to be a correspondingnumber of cm of urine higher than atmospheric pressure. The backpressurecan then be adjusted using, for example, a lever or spring that adjuststhe relative depth of immersion of the distal end of the shunt withrespect to the surface of the liquid it is placed in. Making thisadditional pressure head adjustable inhibits both over-pressurizationand suction of the bladder.

In open channel flow as compared to closed channel flow, pressurized gaspockets cannot form because an open channel has continuous access toatmosphere and is thus continuously “vented”. However open channel flowcan be messy, for instance, if the liquid overflows the open channel andspills outside. On the other hand, a closed channel like a closed tubecontains the liquid and prevents it from spilling and causing a mess butis subject to the formation of gas pockets or airlocks that can thencreate back pressure and impede flow.

Accordingly, in one embodiment of the invention, a general purpose tubewith a quasi-continuous slit 160 running along its length is provided.The slit is quasi-continuous, instead of continuous as can be providedin other embodiments, because there are connecting pieces of the tubingmaterial at intervals to maintain the mechanical integrity andcross-section of the tube as for example in FIG. 16. Such a tube with aquasi-slit running throughout its length would behave like anopen-channel. If a continuous or non-continuous strip of a gas-permeablemembrane is attached to the entire length of the quasi-slit along theinternal and/or external surface, then the tubing is converted into aclosed channel that constrains the liquid flowing through it but iscontinuously vented along its length.

The cross-section A-A in FIG. 16 shows three strips of a gas-permeablemembrane running along the length of the tube with the cross sectionperformed at a location where there are slits. As an alternativeembodiment, the strips can form enclosed lumens as shown in thealternate cross-section, especially if the tube is not vented toatmosphere but to some other desired pressure. The tube would beextruded as for section A-A except that, running next to the slit, therewould be a continuous flange 162 whose free end is then bent over afterextrusion and bonded back to the tube to create a lumen. In theembodiment shown in FIG. 16B, there is a corresponding slot 164 thatruns along the quasi-slit. To create the lumen, the tip 166 of theflange is bent over and inserted into the slot 164 forming a lumen. Theconnection between slot 164 and tip 166 can be made airtight by glue orultrasonic welding. Thus, the tube would offer the benefits of bothclosed channel flow (containing the liquid flowing through it) andopen-channel flow (no formation of air locks). For other applicationswhere the liquid is not water or the gas is not air, the membrane wouldbe selected to vent the desired gas but prevent passage of the liquidthat needs to be kept out.

Accordingly, embodiments are provided that can control outflow andback-flow in drainage systems. In certain embodiments, existing drainagesystems can be retrofitted or directly applied with featuresimplementing the subject context-sensitive flow interrupter and/oroutflow optimization system.

In accordance with embodiments of the invention, methods of venting adrainage tube, methods of providing context-specific flow interruption,fluid outflow optimization apparatuses, fluid back-flow preventionapparatuses, integrated systems to control outflow and back-flow, kitsfor draining a biological fluid from a site in a subject, and kits formodifying an existing conventional Foley assembly are provided.

The terms bag, canister, and receptacle have been used interchangeablyin certain embodiments of drainage systems described herein. It shouldbe understood that the described receptacles can be in the form ofcanisters, chambers, bags, and other structures depending on theparticular drainage system application. For example, in urinary drainagesystems, the receptacle is usually a Foley bag; and in chest drainagesystems, the receptacle is usually in the form of a canister or astructure having a collection chamber.

It should be understood that embodiments described with respect to aurinary drainage system can be applied to other drainage systems andembodiments described with respect to a chest drainage system can beapplied to other drainage systems, and these examples should not beconstrued as limiting a particular drainage configuration to thoseexplicitly described applications.

Embodiments of the invention include, but are not limited to:

1. An apparatus for inhibiting fluid flow along a drainage path betweena drainage collection container and a source of the fluid, the apparatuscomprising: an actuator portion on a section of a drainage pathcomprising a flow interrupter that inhibits fluid from passing throughthe drainage path at the section having the actuator portion; a holderportion that engages the actuator portion wherein interacting theactuator portion with the holder portion of the device changes the stateof the flow interrupter of the actuator portion.

2. The apparatus according to embodiment 1, wherein the flow interruptercomprises a clamp, stopcock, or cuff

3. The apparatus according to embodiment 1, wherein the flow interruptercomprises a normally closed clamp capable of bringing a first portion ofan interior wall of a drainage tube in contact with a second portion ofthe interior wall of the drainage tube such that fluid is inhibited frompassing through the flexible drainage tube, wherein interacting thenormally closed clamp with the holder portion causes the normally closedclamp to open.

4. The apparatus according to embodiment 3, wherein the normally closedclamp comprises a jaw-opening spring clamp having two arms extendingfrom the spring clamp and the holder portion can comprise one or morebrackets or rods defining a receptacle for the jaw-opening spring clamp,the receptacle having a diameter or opposing sidewall spacing smallerthan a distance between the distal ends of the two arms, whereininsertion of the jaw-opening spring clamp into the receptacle causes thedistance between the distal ends of the two arms to decrease, therebyopening the jaw-opening spring clamp.

5. The apparatus according to embodiment 3, wherein the normally closedclamp comprises a resilient deformable material on or within the sectionof the drainage tube, wherein the resilient deformable material causesthe section of the flexible drainage tube to be in a collapsed positionuntil interacted with the holder portion.

6. The apparatus according to embodiment 1, wherein the holder portionis configured to support a drainage collection receptacle.

7. An apparatus for optimizing outflow in drainage assemblies, theapparatus comprising: a mechanical template to shape a tube, themechanical template providing a monotonic downward gradient from a bodycavity or space to a drainage collection receptacle for a drainage tubeshaped with the mechanical template.

8. The apparatus according to embodiment 7, wherein the mechanicaltemplate comprises a peg, groove, or bracket assembly.

9. The apparatus according to embodiment 7, further comprising adrainage collection bag holder affixed at one end of the mechanicaltemplate for hooking the drainage collection receptacle thereto.

10. A drainage assembly comprising: a drainage tube having a pressureequalizing vent, and a drainage collection bag connected to the drainagetube.

11. The drainage assembly according to embodiment 10, wherein thepressure equalizing vent comprises an aperture in the drainage tube anda gas-permeable membrane for venting the drainage tube to atmosphere ora particular vacuum level while blocking liquid from passing through theaperture.

12. The drainage assembly according to embodiment 11, further comprisinga collar around a section of the drainage tube having the aperture. Theaperture and gas-permeable membrane can continuously orquasi-continuously wrap-around an entire circumference of a portion ofthe drainage tube.

13. The drainage assembly according to embodiment 11, further comprisingan external tube extending from the aperture along the drainage tube toan equalizing receptacle that is vented to atmosphere or has an appliedvacuum. The equalizing receptacle can comprise a fluid therein and theexternal tube is controllably immersed in the fluid in the equalizingreceptacle to provide a desired back-pressure.

14. The drainage assembly according to embodiment 10, wherein theequalizing vent comprises at least one inbuilt venting lumen embedded ina wall of the drainage tube, wherein one end of the venting lumen isexposed to an interior of the drainage tube and the other end of theventing lumen is configured to be exposed to an interior of the drainagecollection bag connected to the drainage tube, wherein the drainagecollection bag is vented to atmosphere. The other end of the ventinglumen may comprise an immersion portion for controllable immersion intoa liquid in the drainage collection bag.

15. A drainage assembly comprising: a drainage tube having one or morepressure vents along a portion or all of the drainage tube length,whereby at least one vent will not be occluded by an adjacent body ofliquid during clinical use, irrespective of the orientation orconfiguration of the drainage system. The drainage tube can be part of,for example, a urinary or chest drainage assembly.

16. The drainage assembly according to embodiment 15, wherein the one ormore pressure vents each comprise an aperture in the drainage tube and agas-permeable membrane for venting the drainage tube to a desiredpressure, such as atmospheric pressure or a particular vacuum level,while blocking liquid from passing through the aperture.

17. The drainage assembly according to embodiment 16, further comprisinga collar around a section of the drainage tube having the aperture. Theaperture and gas-permeable membrane can quasi-continuously wrap-around acircumference of a portion of the drainage tube.

18. The drainage assembly according to embodiment 16, further comprisinga venting tube or lumen extending from at least one aperture of the oneor more pressure vents along the drainage tube to atmosphere or to areceptacle that is vented to atmosphere or under applied vacuum.

19. The drainage assembly according to embodiment 18, wherein thereceptacle can be a drainage receptacle of the drainage assembly or aseparate compartment.

20. The drainage assembly according to embodiment 15, wherein the one ormore vents comprise at least one inbuilt venting lumen embedded in awall of the drainage tube, wherein one end of the venting lumen isexposed to an interior of the drainage tube and the other end of theventing lumen is configured to be exposed to an interior of a drainagecollection receptacle connected to the drainage tube. The drainagecollection receptacle can be vented to atmosphere or under an appliedvacuum.

21. A method of optimizing outflow in a drainage assembly, the methodcomprising providing a vent in a drainage path of the drainage assembly.

22. The method according to embodiment 21, further comprising providinga context-sensitive flow interrupter at one end of a drainage tube ofthe drainage assembly at or near a drainage collection bag of thedrainage assembly for inhibiting back-flow of fluid from the drainagecollection bag.

23. A method of controlling fluid flow in a drainage assembly, themethod comprising providing a context-sensitive flow interrupter at oneend of a drainage tube of the drainage assembly at or near a drainagecollection bag of the drainage assembly for inhibiting back-flow offluid from the drainage collection bag.

24. A drainage assembly kit comprising: a catheter; a drainagecollection bag; and a drainage tube comprising a vent. The catheter canalso include a vent. In addition, a sterile venting needle can beincluded in the kit.

25. The kit according to embodiment 24, wherein the vent comprises aninbuilt venting lumen embedded in a wall of the drainage tube, whereinthe drainage collection bag comprises a venting receptacle for receivingan immersion portion of the venting lumen.

26. A drainage assembly kit comprising: a context-sensitive flowinterrupter comprising: a drainage tube portion for affixing to adrainage tube, wherein the drainage tube portion comprises a clamp orstopcock; and a holder portion.

27. A drainage assembly kit comprising a catheter; a drainage collectionbag; a drainage tube comprising a drainage tube portion of acontext-sensitive flow interrupter; and a holder portion of thecontext-sensitive flow interrupter.

28. A drainage assembly kit comprising a catheter; a drainage collectionbag; a drainage tube; and a mechanical template to shape a tube.

29. A method of controlling pressure and fluid drainage in a drainagesystem assembly, the method comprising: venting at least one location inthe drainage system assembly to atmospheric pressure, sub-ambient, orsupra-atmospheric pressure.

30. A method of controlling pressure and fluid drainage in a drainageassembly, the method comprising: venting to atmospheric pressure,sub-ambient, or supra-atmospheric pressure at least one upstream airpocket in a drainage assembly with a fluid filled loop.

31. A method of controlling pressure and fluid drainage in a drainagesystem assembly, the method comprising: obtaining a monotonic gradientin a drainage tubing.

32. A method of controlling fluid flow, the method comprising:automatically opening or closing a flow path interrupter when the flowpath interrupter is engaged in a holder.

The above listed embodiments are merely provided as a sampling ofembodiments of the invention and should not be construed as limiting theinvention to the embodiments listed. In addition, the above numeratedembodiments should not be interpreted as presenting key or essentialfeatures of the claimed invention that would otherwise limit the scopeof the claims.

All patents, patent applications, provisional applications, andpublications referred to or cited herein are incorporated by referencein their entirety, including all figures and tables, to the extent theyare not inconsistent with the explicit teachings of this specification.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. In addition, anyelements or limitations of any invention or embodiment thereof disclosedherein can be combined with any and/or all other elements or limitations(individually or in any combination) or any other invention orembodiment thereof disclosed herein, and all such combinations arecontemplated with the scope of the invention without limitation thereto.

It should be understood that the examples and embodiments describedherein are for illustrative purposes only and that various modificationsor changes in light thereof will be suggested to persons skilled in theart and are to be included within the spirit and purview of thisapplication.

What is claimed is:
 1. A drainage assembly comprising: a drainingcatheter; a drainage tube comprising a first end connected to thedraining catheter; a venting system comprising a venting tube and avalve exposed to an inside of the venting tube; and a vacuum sourceconfigured to apply vacuum to the drainage tube, wherein the ventingtube is in fluid communication with the drainage tube, and wherein thevalve is configured to allow gas to pass therethrough and into thedrainage tube when a predetermined vacuum in the drainage tube isreached.
 2. The drainage assembly according to claim 1, wherein thevalve is a passive valve, configured to allow or restrict flow of liquidor gas when a predetermined pressure threshold value is reached, freefrom the need of an external force or an external mechanism.
 3. Thedrainage assembly according to claim 1, wherein the venting system isconfigured to vent to atmosphere.
 4. The drainage assembly according toclaim 1, wherein the venting tube runs along a length of the drainagetube.
 5. The drainage assembly according to claim 1, wherein the ventingsystem is configured to limit suction at the first end of the drainagetube.
 6. The drainage assembly according to claim 1, wherein the ventingsystem further comprises a gas-permeable membrane for venting thedrainage tube to a desired vacuum, while blocking liquid from passingthrough the membrane.
 7. The drainage assembly according to claim 1,wherein the drainage tube further comprises a second end connected to areceptacle container.
 8. The drainage assembly according to claim 7,wherein the venting tube is connected to the inside of the receptaclecontainer.
 9. The drainage assembly according to claim 1, wherein theventing tube is a lumen that is external to the drainage tube.
 10. Thedrainage assembly according to claim 1, wherein the valve comprises afirst end exposed to an inside of the drainage tube and a second endexposed to the inside of the venting tube.
 11. The drainage assemblyaccording to claim 10, wherein the venting tube is connected to thedrainage tube only at the location of the valve and is detached from thedrainage tube elsewhere.
 12. The drainage assembly according to claim 1,wherein the venting tube is connected to the drainage tube along alength of the drainage tube.
 13. The drainage assembly according toclaim 1, wherein the venting tube is extruded with the drainage tube.14. The drainage assembly according to claim 1, wherein the drainingcatheter comprises: a proximal end connected to the first end of thedrainage tube; and a distal end comprising a sensor for measuringpressure.
 15. The drainage assembly according to claim 14, wherein thesensor comprises a pressure sampling tube for measuring pressure.
 16. Adrainage assembly comprising: a draining catheter; a drainage tubecomprising a first end connected to the draining catheter; a ventingsystem comprising a plurality of vents; and wherein each vent of theplurality of vents is in fluid communication with an inside of thedrainage tube, and wherein each vent of the plurality of vents isconfigured to allow gas to pass therethrough and into or out of thedrainage tube when a predetermined vacuum or pressure in the drainagetube is reached.
 17. The drainage assembly according to claim 16,further comprising a vacuum source configured to apply vacuum to thedrainage tube.
 18. The drainage assembly according to claim 16, whereineach vent of the plurality of vents is exposed at a first end to aninside of the drainage tube, and wherein each vent of the plurality ofvents is exposed at a second end to the inside of a venting tube, andconnects the drainage tube to the venting tube.
 19. The drainageassembly according to claim 18, wherein the venting tube runs along alength of the drainage tube.
 20. The drainage assembly according toclaim 16, wherein the venting system is configured to vent toatmosphere.
 21. The drainage assembly according to claim 16, whereineach vent of the plurality of vents comprises a gas-permeable membranefor venting the drainage tube to a desired pressure or vacuum, whileblocking liquid from passing through the membrane.
 22. The drainageassembly according to claim 16, wherein each vent of the plurality ofvents comprises a valve.